#0A153A

CSS

:root {
  --infinite-night: #0a153a;
  --infinite-night-rgb: 10 21 58;
  --infinite-night-oklch: oklch(0.212 0.073 267.3);
}

.element {
  color: var(--infinite-night);
  background-color: hsl(226 71% 13%);
  border-color: oklch(0.212 0.073 267.3);
}

Tailwind CSS v4

@theme {
  --color-infinite-night: #0a153a;
  --color-infinite-night-50: #ecf5ff;
  --color-infinite-night-100: #dee7ff;
  --color-infinite-night-200: #c7d4f5;
  --color-infinite-night-300: #a8b6de;
  --color-infinite-night-400: #8b9ecb;
  --color-infinite-night-500: #7185b7;
  --color-infinite-night-600: #5f709b;
  --color-infinite-night-700: #4c5a7c;
  --color-infinite-night-800: #36425c;
  --color-infinite-night-900: #252e40;
  --color-infinite-night-950: #141a29;
}

SCSS

$infinite-night: #0a153a;
$infinite-night-rgb: 10, 21, 58;
$infinite-night-light: mix(#fff, $infinite-night, 20%);
$infinite-night-dark: mix(#000, $infinite-night, 20%);

.element {
  color: $infinite-night;
  box-shadow: 0 0 0 2px rgba($infinite-night, 0.35);
}